Stereo Solar

Photos From Installations

2011-10-19T10:00:00.000-07:00

These are photos of houses in Connecticut that I installed PV grid-tied systems on.

New Video.

2011-10-18T01:38:00.000-07:00

Demonstration

2011-10-08T14:18:00.000-07:00

I have developed a board game, and the purpose of it is to display how to design solar electrical systems on a variety of hypothetical sites, estimating the size of the system, selecting the components, and evaluating the annual production of that system. You can check your answers to ensure that your calculations are correct.

After establishing that your methods of calculation are accurate (and by familiarizing yourself with all the parts of a system), you should be able to accurately assess your home for its own solar electrical system. That is the purpose and meaning behind the board game.

Panel Wiring Methods

2011-09-22T08:15:00.000-07:00

The part of the installation often overlooked by system designers is the method in which the panels on the roof are to be wired. If the wires become loose, it is possible that they will fray if wind underneath the array happens to cause the insulation to rub against the asphalt shingles, which is basically as rough as sandpaper.

Aside from that, it's also important to accomplish the following, in your wiring methods:

Use the least amount of wire (cuts down on expenses and voltage drop)
Create the least amount of problems (cuts down on lost time wondering what to plug in).

Think about it. If you have 24 panels, and each one has two 2' leads, that's already 96' of wire, not in conduit, underneath your array. Not to mention that there need to be wires that connect to those leads (the proverbial 'homeruns' mentioned elsewhere in this blog).

These examples show you how to minimize the trouble involved in wiring panels. What I learned as an installer is that there is an art to this procedure. Being an appreciator of the arts, I thought this was noteworthy. So I came up with a neat way of describing how to wire panels on the roof.

Throughout this part, you'll see a yellow arrow, which essentially means "this panel is wired to that one." If you wonder which lead is connected, the answer is at the end of the string.

You'll find a square with a number at the beginning of a string. This number represents the 'homerun' which is a lead that goes to the combiner box. The grey colored square represents the grounded conductor of that string (see grounded conductor article for more info).

At the end of a string, you will see a red box with a corresponding number. That's the homerun for the ungrounded conductor. Each set of arrows leads from a grey square to a red square, indicating which panels are wired to which other panels. So here we go.

Here is a simple roof. The panels are wired in series of 8, as you can see, which is fortunate because they're also in rows of 8. How convenient! These are the types of situations that an installer generally likes to see, because it means that the process of preparing the roof for wiring is quite simple, compared to the next example. As you can see, all of the grounded conductor homeruns are on the left, and all the ungrounded conductor homeruns are on the right, at the end of the rail.

Let's take a look at a more complicated example.

Here's a weird roof. This one has all kinds of odd, peculiar stuff going on. The two rows at the bottom need to be connected to rows above. The method described in this illustration is far preferred, compared to other possible methods, for a few reasons.

It doesn't involve lots of 'up & down' - - connecting panels to the ones above or below can make the wiring much more difficult and prone to problems later (and by later, I mean 25 years +). Nothing makes an installation last longer than tight wiring from one panel that is directly next to another panel.
It doesn't involve any connecting parts or diagonal wiring. Panels generally can't connect diagonally without some stress put on the wire.

This is an example of four panels that need to be wired together. Despite how similar each example may appear, the one on the right is twice as easy for an installer to wire, and half as likely to have problems, because of fewer vertical crossings. All that's involved is a different placement of the grounded conductor homerun in each example.

USE-2 and THHN: WIre Insulation Types

2011-09-20T08:43:00.000-07:00

Source: NEC

RHW-2 in this table is listed, and it's the same as USE-2, which is an outdoor-insulated wire, recommended to connect to the panels by all professionals in the PV industry. Here is a table which states the number of said wires inside of EMT conduit. Solar Panels have USE-2 wires coming from their j-boxes, and the connectors are made to create water-tight seals onto that type of outdoor insulation.

In this table, it's noted that 8 of such wires can fit inside of 1" conduit, meaning that you can have a total of 4 strings entering a 1" conduit, or else you will have to up-size to 1 1/4, which will allow you to have 13, or a maximum total of 6 strings.

USE-2 is "Underground Service Entrance" and you can buy it from nearly any source of PV supplies. It's coated with a blood thinner which acts as a way to keep animals from eating it (it's essentially covered in animal poison) so be careful with eating after you have handled USE-2 wire. It's also UV resistant, and because of all this, it's much thicker than THHN wire, which is why fewer wires will fit inside of conduit. You can run this type of wire from the panels to the combiner box.

Source: NEC Table C.1

By comparison, THHN and THWN and THWN-2, all conductors rated to be indoors or inside conduit, can fit up to 16 of the same #10 AWG conductors in 1" conduit. It's also less expensive than USE-2, making it the wire of choice for installers to have inside of conduit.

Source: NEC Table C1

Installation Chronology (Overview)

2011-09-20T08:11:00.000-07:00

"There's only one way to do things correctly, and a whole bunch of ways to do things wrong." -Catfish, Installer

Catfish, our imaginary installer, knows the right way to start a project. In fact, he's self-considered to be right about everything all the time! So, if you arrive at someone's doorstep for the first time, and they've never met you before, and all you have are a bunch of photos of their house and the system design plans, what is the best way to go about performing an installation?

1. Consult the Property Owner and Confirm Plans
Walk with the homeowner to every part of the house and show them, physically, where you plan on mounting the inverter. Make sure they verbally OK it with you. That way, they can't, in good conscience, complain and say they wanted it elsewhere later. Then, explain the path you will run the conduit. Ask if they had any special considerations. Ask where the bathroom is, and tell them that you and your installer crew will need access to it during the installation *unless they want to give you guys a porta-potty, which is unlikely. Make sure they see the roof layout so that they know how many panels, and roughly what it's going to look like.

2. Set Up Safety Equipment and Ladders, Mark Out The Roof.
After they are entirely on board with the plans, then begin to set up your ladder and harnessing equipment with the work crew. As a lead installer, you should oversee the set-up of all safety equipment, and even the placement of the ladder can be considered part of your responsibility to ensure safety. Once the ladder is set up, mark out the roof with a crayon, to determine the position and length of the rail. I have a special set of symbols that I recommend. Use the same symbols so that people don't get things confused.

3. Construct the Conduit Run.
If you are working in 2 teams (a roof crew and an electrical crew), and you're the lead installer, it's likely that you will be doing the electrical work, and the other guys will be doing the structural stuff. Don't start your conduit run on the roof just yet, because if you mess up and it ends up not where you want it to be, either directly in between panels (obstructed by the frames) or outside of the array, it'll be very difficult to cover up the mistake. Begin making your conduit holes into the house at the point where the conduit will be entering and exiting the structure, depending on your plan. Start anywhere you want, but step 1 is building the conduit run while the roof crew starts finding rafters and marks the placement for the footings. Complete the conduit so that it attaches to the disconnect in the basement, or to a wiring trough. Check with the guys on the roof. By now, you can determine a suitable place to complete the conduit run through the roof. Pilot into the attic with a long bit, trying to find a point just far away from a rafter that you can drop your conduit into the roof and fasten it to the inside of a beam. Check the position of your pilot hole from inside the roof to ensure that it will work with the conduit run. Adjust, if necessary, sealing any pilot holes that you should make. Use a flashing (see a more detailed look at this procedure).

4. Construct the Mounting System (residential roofs)
Assuming you're installing on a traditional roof, and you have a team of trained workers, this by now must be routine to you. Read [here] if you want a more detailed look at this procedure. Make sure that you are using the correct number of footings.

5. Wire the Roof
This is where experience really becomes necessary. You have to map out the positive and negative ends of each string. You also need to ground everything. Make the USE-2 wires long enough to reach where they're going to connect to the panels, and then also long enough to make it into the combiner box with enough extra length (but not too much length) to connect to the parts inside the combiner.

Connect the wires to the parts inside of the combiner box, and add the MC-3 or MC-4 connectors necessary on the roof to connect the wires to the panels. Make sure that you're using bare copper #6 on the roof, and connect it either with a copper split bolt or a irreversible crimp as it exits the conduit LB that is sticking out of the roof. Follow the rules of grounding!

6. Pull Wire From Combiner In Attic To Disconnect In Basement
I came to a point where I wasn't really using "combiners" to make parallel connections, because I found there to be less voltage drop when using multiple #10 conductors rather than fewer larger conductors, in most cases. Still, it made sense to have a J-Box near the roof, just to transfer the wire types from USE-2 to a more conduit-friendly type of wire, namely THHN-2 or similar. In any case, connect all the wires all the way from the roof to the basement. "Tie in" the wires to the terminals in the disconnect, all the way to the inverter. Follow the rules of "grounded conductor wiring."

7. Wire the AC Side.
If you have a PV License in Connecticut, technically you're not permitted to perform this part of the installation, and you really shouldn't because your test didn't cover even the basics of AC wiring. So I'm not going to get into the details of this. The basics are that it goes: Inverter, meter, outside disconnect, service panel. If there are multiple inverters, then it goes inverter 1 / inverter 2, subpanel, meter, outside disconnect, service panel. Don't even ask about lineside taps. You can use double-insulated (romex) wire for this part of the installation because it's after the inverter, no longer DC current.

7. Complete the Wiring and Perform A Preliminary Visual Inspection
Make sure that everything is connected, and everything is off. Perform continuity tests if you wish. If you are thorough, there shouldn't be any problems. It's infinitely safer to complete all the wiring (and also adherent to the NEC code) to make sure that all of this has been done entirely before wiring panels, because once a string of panels has been installed, the wires become live and there's no way to really shut it off. Make sure all your fuses are in, and be sure that you are using the right fuses (see panel specs for that information).

8. Prepare and Install the Panels
Always last, but never least. This should always be the final stage of your installation.

Here in the early part of the 21st century, we haven't figured out not to use conductive metals on the roof, so even the panel frames are aluminum and need to be grounded.

To prepare the panels, use an anti-oxidation gel (like "nolox" or some crap like that). Fasten each nickel-plated beaver tooth ground lug to every panel, using a stainless steel screw, a washer that will bite into the paint of the frame, and a nut behind it to keep it in place. That's the official way to do it, according to all the grand-daddys of solar such as Bill Brooks and John Wiles. Add stainless steel "S-Clips" as well, to keep your panel wires from touching the roof.

As you connect the panels, follow the map that you made in step 4 (if it's not soaking wet or torn into pieces or somewhere in the van). If it's a complicated roof and you lose the map, there will be trouble! Be careful, stay roped in. Once the roof is complete

Following This Order
This manner of conducting installations will provide you with the least number of problems with things not timing correctly. There's no better order of chronology. This particular order of things keeps both the roof crew and the electrical crew working in tandem. It makes everybody available for panel time (all hands on deck) and leaves nothing left over once the panels have been installed.

Installers: Any tips, suggestions, questions, disagreement, or otherwise? Please say.

Calculating Hold-Down Strength

2011-09-19T12:00:00.000-07:00

In order to ensure that your PV array is not going to fly away, you need to effectively ensure that it's connected adequately to the structure it's installed on.

That's done by using a chart like this one, which is provided by the Standard Handbook For Mechanical Engineers:

Each screw, usually a lag that fastens into the support of a rafter inside of the roof, has a different diameter. Different types of wood have different resistance strengths. Each amount of allowable withdrawal is determined by 1" of threading inside that particular kind of wood. For example:

A 3/8" lag through Southern Yellow Pine that is 2" long will have a withdrawal strength of 381x2, or 762 lbs.
A 1/4" lag through Douglas Fir that is 3" long will have a withdrawal strength of 232x3, or 696 lbs.

Let's also say that the plywood that separates the roof surface from the rafters is 3/4" thick. You would need to subtract that 3/4" from the length of the screw.

So how do you estimate whether a system has enough support to keep from flying away? Wind speeds with force that is greater than 75 lbs/ft will cause the glass to shatter, thus creating a limit to how much hold-down strength the array needs.

You can take the area of your array, in square feet. Multiply the 75 lbs/sq.ft by a safety factor of 4. That will help you determine that the array will require 300 pounds per foot of hold-down strength.

Let's say that there are 30 solar panels, each with an area of 15 sq. feet. That's 450 square feet.

Determine the number of feet, attached with 3/8" screws 3" in length, that are required to hold the array in place to satisfy the requirements of hold-down strength. The wood type is Southern Yellow Pine.

450 x 75 = 33,750 lbs hold down strength required.

Each screw is 3" at 3/8" diameter in yellow pine (381 x 3 = 1143 lbs per screw).

Divide 33,750 by the 1143 per screw and you get 29.5, which is essentially 30.

This particular example requires 30 footings in order to satisfy the requirements of hold-down strength.

Use this formula and these calculations for any array!

Variables

You will find the example to use 75 lbs per square foot as the panel's weight load. Find the information on panel specifications as listed by "load resistance." Officially, you must also account for the depth of the plywood as not included by the amount of thread that is actually fastened into the rafters.

Counter-Ballast Systems
Instead of using the hold-down strength of screws, just calculate the weight of your counter-ballast (usually cinderblocks) and then determine how many cinderblocks you need, with the same formula. (Square area of array, pounds per square foot of required hold-down strength determining number of required blocks).

References
Nabcep Study Guide
Handbook For Mechanical Engineers

Site Survey: 2 Roof Surfaces, Different Orientations.

2011-09-19T08:46:00.000-07:00

A Site Survey is an estimate that contains the following information:

The size of a system, in Kw, based on the number of solar panels that can fit in the available area.
The type of recommended system components that will work with that number of panels.
The annual power produced by that system, based on regional factors.

Here is an example of a site survey, which contains all of that information.

This image was made after all of the roof measurements were made. This particular roof contained two separate roof surfaces, one facing southeast, and the other southwest.

There were areas of shading, one from a chimney and the other from an adjacent house. Those areas were marked with a darker color. This image was produced using Macromedia Flash 8, but the measurements were produced with a ladder and a tape measure. The orientation of each roof surface was also noted, and the shading was determined by using a pathfinder.

Here are the actual pathfinder readings. As you can see here, the perimeter indicates that during the shorter months of the year (November - February), there were some issues in the afternoon with the next door house, and the chimney. That's why a 10% shading derating factor was utilized in the total estimate. The Pathfinder is a useful device and they're relatively expensive, for a dome-shaped piece of plastic, although they are cheaper compared to electronic devices which produce the same information.

Once the size of the system was determined using the available area on the roof, the next step was to estimate the power that the system would produce over the course of a year.

Since the system was facing southeast and southwest, respectively, each array faced a .96 derating factor (for not being perfectly south at 30°), and then an additional 10% was subtracted from the panel STC for shading.

The wattage rating of the selected panels (Sunpower 230's) were multiplied by their number (there were 18 on one roof, 24 on the other).

Other factors, such as irradiation in the region (in CT, it's 4.5) and the standard 75% derating factor was applied. The result was an annual estimate of 28 kwh per day, saving the homeowner an average of $180 per month.

One Line Diagram. Grounding Not Displayed.

The Book!

2011-09-16T09:47:00.000-07:00

LineLoad by Ian Applegate | Make Your Own Book

Design your own system from scratch, using the information on this blog.
It's not that tough! You can even make your own board game.

Solar is not that difficult to understand. The awesome photos in the background were taken by the same installer who wrote all the content. Using the knowledge base from 3 years of field experience, Sunpower Certification, State Certification, and references recommended by NABCEP, this book gives the average homeowner a good sense of whether a photovoltaic system will be enough for your electrical energy needs.

There's a lot of talk about whether it's financially worth it to invest in Solar energy. I don't think there could possibly be a better thing to invest in, this day and age. Even the stock market can't guarantee the returns that a PV system can. It's inevitable that electrical costs are going to rise in the future. There is nothing more comforting than knowing that your price has been locked in the payback of a system that you bought years ago.

PV panels can last up to 50 years, and some are guaranteed to last with lengthy warranties of 25 years provided by some manufacturers (namely, Sunpower). Inverters usually last 10-15 years.

There's never been a better time than now, and the technology is ready for consumption. Many people are led to believe that it's not ready yet, but there are plenty of homeowners with systems that work great, and have their energy prices locked for probably the rest of their lives.

Check out the book and think about investing in your photovoltaic system!

System Design Checklist

2011-09-14T09:55:00.000-07:00

Let's say that you're getting ready to prepare your home for a PV system, and you are doing research about how to go about that process.

There's a ton of information online about Solar Electricity, not all of it useful. I hope that you find the information on this website to be an exception, because my intent really isn't to sell you anything. I really just want to share the things that I've learned from building and designing systems. I want you to feel confident that this will work.

If you are interested in assessing your own home, and you feel confident in your ability to take measurements, this is what you can do:

Collecting Data

Determine your home's orientation, using a compass.
Find the southernmost facing roof surface, and determine its pitch with an inclinometer.
Measure the area of that roof surface.
Pick a type of solar panels, and use those dimensions to determine how many panels will fit

Additional Data:

What is the busbar rating of your main service panel?
What is the main breaker rating of your service panel?
What is the spacing of rafters in your roof? Is it a truss system?
How much shading is in your environment?

Estimating Power

Once you can determine how many panels will fit, you can then multiply the number of panels by their STC wattage to determine what the wattage of your system will be.

For example, if you can fit 30 x SPR-230 panels, that's technically 6900 watts, or a 6.9 KW system.

Next, take your 6.9 KW number and perform the following calculations:

Subtract the percentage that will be shaded. If no shade, skip this step.
Subtract the percentage that derates the system by orientation and angle.
Take 75% of whatever's left.

Let's say that your 6.9 KW system has 10% shading, it faces Southeast, and the roof is 30°.

Southeast at 30° is 96% efficient. Also accounting for your shading, the system is valued at 6 KW.

The 75% factor is an industry-standard practice recommended by Sunpower and other agencies, to keep your estimates from being too high. Typically, other factors such as dust and debris on the panels, as well as voltage drop in the wiring and inverter efficiency, will subtract from the production of the system. By taking a conservative estimate, you allow yourself some room.

Your new rating is 4.4 KW

Next: Factor Your Insolation

Depending on the part of the country you're in, this system will perform differently. You can find this information from the National Renewable Energy Laboratory Red Book. Most of the country is between 4 and 6 w/m/2. So let's just say we're in a part of the country that has a factor of 5.

4.4 KW multiplied by 5 w/m2 is 22.
That number essentially represents the average amount of KWH per day that you can expect from your system on an annual basis.

Of course, that's going to fluctuate depending on what time of year it is, but that's why NREL provides annual averages for irradiance, because it's the best way of estimating your system's potential, with all the varying factors of sunlight energy potential throughout the year.

22 KWH per day is the most important number that you can derive from this, because it will help you determine the financial value of the system. It will also help you determine if the size of the system matches your electrical use.

This formula is used standard by professionals in estimating the annual production of the systems that they sell to people across the US. You can try it yourself if you'd like. Remember to account for your own factors, as listed by the information that you gather about your home's orientation, angle of your roof, the area shading, your region's irradiation, plus the type and number of solar panels that you wish to install. Good Luck!

Determing Shade

2011-09-14T09:00:00.000-07:00

Shading can be bad for a system. There are different kinds of shading, which are determined by the level of focus of the shade. For example, "soft shade" is from far-away objects, whereas "hard shade" comes from objects that are closer to the solar panels.

If you're trying to determine just how much shading is going to occur on your roof, then you can get into using a device like a Solar Pathfinder.

Here are what obstructions appear like, when you are using a Pathfinder:

If you don't have a pathfinder, it would be not as accurate but you can guess your shading. Many people seriously considering systems will effectively analyze their roof for shading just by observing it year-round, and you can't beat that. If you check right around the holiday season, to see where all the shadows fall on your roof, then you will probably have an idea of the worst of your shading issues.

Or you can get a pathfinder! It's entirely up to you.

Where Should I Put My Inverter?

2011-09-14T08:50:00.000-07:00

If you have an inverter, then you're probably thinking, where should I put it? The answer is not in any old place! There needs to be a specific place for it to be installed.

The illustrations below correspond with the circles in the illustration above. To summarize, you want your inverter at a location where it's not near any fuel storage, not in direct sunlight, and typically with the rest of your home's electrical equipment.

Is My House Good For Solar?

2011-09-14T08:42:00.000-07:00

Some homes are better suited for solar electricity than others, but every home can have solar panels installed on it.

It does depend on how much you're willing to change your situation, if the situation is not ideal. Even if we installed solar electrical systems on the 25% of homes that are completely ideal, wouldn't that make the world better? Of course it would!

The factors that most determine a home's ability to produce its own solar energy have much to do with its orientation and angle, as well as shading. Solar panels will work anywhere, but they need to be in a place where they can receive direct sunlight, year round.

Trees can shade your panels, causing your system to lose power somewhat. So can other obstructions on your roof, such as vent pipes and chimneys.

Are your shingles in good shape?

Don't get solar if your roof is all busted and your chimney is falling down. Fix your chimney and replace your roof before you consider getting solar panels, otherwise every installer is going to look at your house and say, "No way! We're not going to be responsible if there's a problem with it leaking because of your old, cruddy roof."

Is your house's electrical system sufficient?

If your home contains wire that is insulated with cloth, then chances are you need to have an electrician come in and rewire your house. If your service panel looks like a ball of yarn that your cat was playing with, then you need to have your house rewired. However, there is a general rule about service panels which determine whether your house is OK for solar.

Is your house facing the right way?

If the axis of your house runs in such a way that your roof surfaces face east and west, instead of north and south, it will compromise your energy somewhat. For a list of those factors in the northeast part of America, check out this efficiency table:

this information is from NREL

As you can see with this table, if your house faces East and it's at a 30° angle, your solar array will only be able to produce 85% of what it's rated for. If your roof can fit 4kw of panels, then, you can only expect your power to be 85% of 4kw at max, which is 3.4 kilowatts. That's not too bad, anyways, for a roof that many professionals will tell you is facing the wrong way.

It's not facing the wrong way, exactly. It's just not facing the ideal way. But that's okay, you can still get a system. This chart just tells you what to expect.

You can survey your own home for solar!

Fun Macintosh Facts:

pressing shift+option+8 will produce the degree ° symbol

AC / DC

2011-09-14T08:18:00.000-07:00

It's not just a cheesy band from England who played weird fast-paced music using weird voices.

The photoelectric effect is only able to produce DC power. Your home works with AC electricity. In order to change that power over to something your home can use, it requires the use of a device known as an inverter.

This page will explain a bit more about the differences between AC and DC electricity.

Alternating Current

AC is "Alternating Current"

AC electricity is manipulated using coils to induce a current that fluctuates from + to - in voltage at a certain number of times per second. Meaning that 120v AC actually fluctuates from 120v+ to 120v- at a rate of 60 times per second (60 hertz).

Conductors

With AC current, you can complete a circuit with one conductor and a neutral, which does not conduct electricity. The two-prong plug that goes into the wall everywhere you go? One of those is the neutral, the other is a "line."

In a home, most devices are 120v AC, meaning that it is using one line. Some devices are 240v, thus using two different lines to combine their voltages. Inverters are typically 240v.

Benefits of AC Electricity

The main reason AC power is so popular is because it travels better over long distances since it is able to be "stepped up" and "stepped down" using transformers. That's why the grid is AC power.

However you'll notice that many of your devices at home contain power adapters which convert electrical energy back into DC again, because many electronic devices work using DC power.

Direct Current

DC power is direct current. It does not fluctuate in polarity like AC power, nor can it operate with a single conductor. It requires a positive and a negative wire in order to operate.

Without a way to induce AC current, electrical components like batteries and solar panels will only generate DC power.

Additional Reading:Grounding

External Links:
PBS Explains This Same Concept

Kilowatt

2011-09-14T07:57:00.000-07:00

A Kilowatt is a measurement of electrical energy.
It is similar a mile-per-hour rating.

When a system is described as a 5 kilowatt system, that means that it is estimated that it operates at 5 kilowatts per hour when it is at full power. That's not an indication of how much power it will generate every hour, but what it's rated at its very best performance.

Determining the kilowatt rating of a system usually involves multiplying the STC wattage of the panels by the number of panels included in the system.

Coming Soon: exercises

(illustration)

Residential Roof Conduit

2011-09-13T14:18:00.000-07:00

If solar panels contain lots of electrical wires, how do they get from the rooftop to the basement?

The answer is conduit. Wires from solar panels need to be inside of metal or plastic pipes. For residential grid-tied systems (what this website primarily deals with), these conductors could be anywhere between 250-550 volts DC.

According to a logical interpretation of NEC 690, if the conduit is indoors, the wires must be inside of EMT, which is metal conduit. If it's outdoors, then it can be in PVC, which is plastic tubing.

The size of the conduit depends on the circumference of the conductors and the number of wires within. Most residential systems that I've installed tend to use 3/4" or 1" conduit, and those have been around 4kw or 5kw. Interior conduit runs typically look much better than ones that run on the outside of the house because they're much more concealed.

In the image you see here, there's a rigid piece of pipe coming through the decking of the roof. Note how it's right against a beam. It's strapped onto the beam using a rigid strap. Then, it goes to an LB pullpoint connector, where the rigid pipe is threaded onto one side, and a EMT connector is threaded into the other. From there, the conduit run continues throughout the home, where it will eventually make its way towards the basement, either by going across the attic to a vertical exterior wall, and then down to the basement, or perhaps through an interior chase, if one exists.

Performing This Task

Making any hole on a roof is a daunting task, especially one large enough to allow conduit to pass through. The conduit entrance will be the largest hole on the roof that you are going to make.

1. Select a spot that will be beneath the system, preferably at an ideal point in the attic to enter. It's okay to have a pull point under an array, like an LB, but you can't put any kind of junction box under there (because of access restrictions).

2. Once you have selected the right area, find the beams. Pilot next to a beam. Check the interior and verify that this is a good spot. Try to make the pilot hole at a point in the middle of a shingle row (not directly above a seam between rows). Once it's verified, get your hole saw out. Pick a hole saw size that is slightly larger than the conduit (for example, if 1" conduit, use 1 1/4" and for 3/4 use 1 1/8" and so on). Get through all of the shingles and the plywood beneath.

3. Now you got a big hole in your roof. That's not such a big deal. Cut the semicircular shape out of the shingles so that the flashing can fit snugly underneath. Get your cat's paw or similar tool out, and loosen up the shingles and remove any nails that will hinder the flashing from fitting all the way beneath the shingles.

4. Get your LB with the threaded rigid conduit attachment. Make sure it's long enough that when it drops in, the pipe will be lower than the beams. For most homes, this usually means getting an 6" piece, a coupling, and then either a 4" or 2" piece of threaded rigid pipe.

National Rebate List

2011-09-13T11:40:00.000-07:00

There is a Database of State Incentives For Renewables and Efficiency. It's called "DSIRE" and they have their own website, which lists currently all rebate funding for every state in the United States.

Click Here To Enter That Database.

Meter

2011-09-12T11:40:00.000-07:00

A meter measures kilowatt-hours.

If a meter is connected to an inverter, it will measure the number of kilowatt-hours produced by that inverter.

Typically, meters are wired between the service entrance and the main service panel, and they indicate how much power the house has used. Utility companies use meters to figure out how much to bill you.

The meter in this picture is a "Net Meter." Note the red sticker on the bottom right. Also notice that there is an arrow pointing to the left, underneath the number "4" on the LED screen. This is indicating that the meter is actually running backwards, counting down the number of kilowatt-hours that the house has consumed. In effect, Net Metering is a way to get your utility company to buy your clean power. Many homes do this.

Equipment Grounding

2011-09-12T11:36:00.000-07:00

In a solar electrical system, everything needs to be grounded. That means that there needs to be electrical continuity with every part of the system, including all of the rails on the roof, and every panel frame.

Code Rules About Grounding
The NEC requires any unsheathed ground wire to be #6 AWG or the size of the largest conductor. It also insists that ground wire outside of conduit must be unsheathed, therefore all ground wire on the roof is #6 AWG. Many installers will continue the #6 size ground wire all the way to the inverter.

After the ground wire has effectively connected every part of a system, it makes its way to the grounding electrode conductor terminal in the inverter. Then, it goes out to a ground rod.

The color of ground wire is green.

Ground wire from the roof, connecting to the combiner box
on a bus bar, then continuing to the inverter

Split Bolts and Acorn Clamps, used for grounding

Angle

2011-09-12T10:49:00.000-07:00

Angle refers to the angle of the surface you are installing on.
0° is considered flat, or horizontal. 90° is vertical.

Most roofs are between 15° and 40° and the point where a roof becomes unwalkable is between 35° and 40°, depending on the individual's ability to balance.

Roof angle affects your overall system production (see efficiency table).

Orientation

2011-09-12T10:46:00.000-07:00

Orientation refers to the direction in relation to the horizon that you are facing.
South is considered 180° and North is considered 0° when discussing orientation.

Orientation affects your overall system production (see chart).

Reading Panel Specification Sheets

2011-09-12T08:59:00.000-07:00

Every Solar Panel not made in Jim's basement is UL listed, meaning that it contains lots of data pertaining to how it performs in a laboratory. This article is going to explain what all that stuff means.

Here is the spec sheet from one of my favorite solar panels, the Sunpower 230-watt panel (*Spr230).

Underneath "Electrical Data" you're going to find that it says "Measured at Standard Test Conditions (STC) irradiance of 1000/m2, air mass 1.5g, and cell temperature of 25°C." It's basically the conditions under which all solar panels are tested in order to get unbiased information so that their performance can be compared to those of other manufacturers.

So let's get into what all of these numbers and abbreviations stand for, and how to understand them.

Pmax is the maximum wattage of the panel in the conditions described (STC).
+/- 5% means that it could be 218w, or it might be 241w, and that's called module mismatch since not all solar panels are created with exactly the same identical properties.

Vmp is the voltage at maximum power, while the panels is under load (connected to a system).
Imp is the current (I) at maximum power, also while the panel is connected.

Voc is the open circuit voltage of a panel. That's when you connect each lead to a voltage tester. It's a theoretical voltage which could occur if something bad happened to the system. VOC is used to determine the maximum number of panels that you can wire in series.

Isc is the short circuit current of the panel. It's the reading you get, under STC conditions, where the negative lead is plugged into the positive lead of the panel and a current reading is taken. This helps determine the size of the fuses that you will use for your system later on, and also helps you determine the size of your DC Disconnect.

Maximum System Voltage is a rating determined by UL, and it has more to do with code requirements than anything else. Remember Voc? It can't be greater than 600v in the US.

Series Fuse Rating is the size of fuse that is required for the string.

Peak Power per Unit Area has more to do with the amount of space on the panel being consumed by solar cells than anything else.

CEC PTC is the California Energy Commission's rating of the solar panel's ability to produce energy. Most of the stuff on this website is with the STC ratings, not PTC which is a different test, although many rebate programs will account for the amount of money that can be granted to a project based on the PTC.

Temperature Coefficients tell how the power changes under different temperature situations. in this case, the voltage increases by 132.5 millivolts (or .132v) per °C. This statistic is also used wiht the Voc to determine the maximum number of panels in series.

Facts About Grid Voltage & Inverters

2011-09-11T14:48:00.000-07:00

Background: Voltage

Inverters are usually 240v devices. However they're a little more sensitive than the rest of the electrical devices in your home. An SMA inverter will shut off if the power from the street deviates by more 10%. In other words, if Line 1 from the street exceeds 132v, or line 2 is low, your inverter goes back into standby mode.

What does this mean?

Some homes receive "dirty power" from the grid, and that's not because it's produced by burning fossil fuels. This means that the power coming into the home isn't a clean 120v line 1, 120v line 2, at exactly 60hz (cycles per second, see AC). This will damage your electronic devices over time, rendering your TV, or computer, inoperable (ever experienced an event where your device just won't turn on?).

Clean and regulated power is better for your appliances. Inverters produce only the cleanest power, literally. It's precise in it's output.

I have had incidents where homeowners called Paul's company to say that their inverter was shutting down. As it turns out, their local utility network was out of wack. We got their provider to start delivering better power, meaning to regulate their varying transmissions.

I will revise this article later. I'm writing it on a phone.

Watt

2011-09-11T11:25:00.000-07:00

A watt is a measurement of electrical energy. You can use watts to measure production and consumption. Wattage is a combination voltage and amperage. A thousand watts is called a kilowatt.

See Also:
Watt-Hour

Daily Solar Energy Production

2011-09-11T11:18:00.000-07:00

A solar electrical system will vary in the amount of power that it produces over the course of the day. That depends on the following factors:

- What time of year it is
- What time of day it is
- How much cloud coverage there is that day.

That said, you're going to get a different amount of sunlight at the same time of day depending on the time of the year, because the days are shorter in the winter, and the sunlight is at a different angle throughout the day.

The illustration that you see here shows you how the position of the sun, and cloud coverage, changes the percent of solar electrical energy being produced over the course of the day.

It's a pretty good illustration, I think.

Inverter Review

2011-09-11T10:57:00.000-07:00

I've mounted, wired, and commissioned probably a couple hundred inverters made by several manufacturers, and on top of that, I've also troubleshot a fair share.

With that experience, I can tell you what I think are the best inverters for your grid-tied installation. This is my unbiased opinion, and what's factored in most is which ones seem to require the least attention once they're installed.

Most inverters have a lifetime expectancy of 10-15 years, provided they're not installed in a bad place or the system they're connected to is the right size. None of the inverters that I've installed have been working for that long, so I can't tell you if any of these will exceed those expectations, but some inverters seem a bit more durable than the others, based on my troubleshooting records.

Here are my reviews of the 4 most common inverter manufacturers.
These are listed in order of least to most preferred.

Xantrex.
These things are kind of cheap and they break frequently. Sunpower used to sell them as part of the system with their panels, but that didn't last, because they had to recall a whole bunch of them.

Solectria
These are made in the United States, which is nice. But they do seem a little cheap, and their commerical inverters have a tendency to break (their cores go bad, it's a common problem).

Fronius
Also built in the USA, these guys are reliable and easy to swap out parts if something goes wrong so that you don't have to re-install the whole thing.

SMA
These are by far the most durable of all inverters available on the market, as far as I can tell. I've never had to replace or repair one. The solid-state ones are really heavy, and that's because their built-in transformers weigh a ton! (actually about 150 lbs). That said, I typically recommend these before any of the other inverters because I trust them to last.

You should really do your own research about inverters, as well. Links to all of the various manufacturers are listed above in their names. Efficiency is just as important as durability, and with none in the field actually installed for the duration of their lifetime expectancies, it's really anyone's guess as to which will last the longest. My guess is the SMA transformerless inverters.

See Also:
Inverter Placement

Watt-Hour

2011-09-11T10:26:00.000-07:00

A watt-hour is a unit of electrical energy, often used in determining cost for electrical usage. It is the result of one watt being consumed for the duration of an hour.

The formula for watt-hours is simple. If a 10-watt device is running for an hour, then that device has consumed 10 watt hours. If it is a 100-watt device, and it has been running for a half-hour, then it's 50 watt-hours of consumption.

Watt-hours are measured by electrical meters.

Parts of a PV System

2011-09-11T07:17:00.000-07:00

There are only a limited number of components necessary when installing a solar electrical system. If you understand what those parts are, and what they do, then you can begin to learn how to select parts that work together. It's simple!

If you feel overwhelmed by the complexity of the world, just remember that you need to learn more about the parts that make the world such a complex, unique place. The parts are simple, and they have recognizable characteristics.

All you need to build a solar electrical system that is grid-tied and supports your home energy needs! Right here!

So here they are. The Solar Panels are just one step in the process of designing a complete solar electrical project. They run to a "combiner box" which is where electrical parts perform some math duties on the voltage and amperage before heading off to the inverter.

The inverter is where all your AC power is made. It's wired into your main service panel just like anything else in your home.

Inverter

2011-09-08T17:15:00.000-07:00

The inverter converts solar DC current into AC power that your home can use. It's a central part of an installation, because all solar panels generate DC power, and the grid is AC. There always must be an inverter.

[Recommended Manufacturers]
[Think Like An Inverter]
[Calculations]

EMT Conduit

2011-09-08T17:02:00.000-07:00

DC Solar electricity inside of residences in America are required to be encased in EMT, which is metal conduit. It becomes a challenge to weave conduit in and out and between many of the commonplace things you encounter in the average home. A good electrician can work wonders with a piece of EMT, though there are a few simple rules to remember when dealing with it.

You can't exceed 360 degrees in bends, with any pipe run. In order to "reset" the bends in your pipe run, an electrician can use a "pull point" which can be an "LB" or a J-box of some kind. Fun stuff.

EMT is necessary inside of homes for solar, because in the event that there is a fire in your home during the day, the idea is that a fireman cutting through a wall with solar current running through it will not get electrocuted (nor you or anyone in the future who decides to do some renovations).

The NEC is designed to prevent fires, primarily, but it also keeps people from getting electrocuted, which is also quite useful. Make sure that you have a licensed, experienced electrician on site, constructing your PV system's conduit run.

UN Says World Could be 80% Renewable by 2050

2011-09-08T16:55:00.000-07:00

Recently, the UN stated that we could be 80% renewable by 2050. In order to make that a reality, however, the broad scope of human beings in the world need to be ready to accept and understand the new technology brought upon us. Being responsible for your own power generation is a concept foreign to many of us, because most of us have our electrical energy produced somewhere else, on some remote site. Are you ready to produce your own electricity?

I hope that through this website, and others like it, together we can prepare for that kind of a future.

This page indicates ways of generating power. Some are clean, others less so. No matter what, a human being is going to have a carbon footprint because none of us are so light that our breath does not enter the air, any less than our feet touch the ground.

That said, consider all of the types of utilities available. Did you know that in 2010, the United States uses less hydroelectric power than it did in 1997? In effect, we are less renewable than we were back then.

If the US Federal government were to manufacture its own solar panels, there would be no cause for excessive price due to corporate profits. People could buy them directly with "tax" money. Currently, that's not how the system works, and it may never work that way. If we've learned anything by watching the way that this century has unfolded, the separation between "have's" and "have-not's" is becoming more clear and distinct by the very concept of ownership that exists between those two states.

Standard Test Conditions

2011-09-08T16:48:00.000-07:00

STC
In order to rate solar panels fairly, the Department of Energy, in conjunction with Underwriter's Laboratory, have developed a system for rating panels so that the consumer is getting unbiased and accurate information about panel performance.

All panel power ratings are determined by their performance in laboratories under Standard Test Conditions, in which a light with the strength of 1000 w/m2 flashes on a panel. The temperature of the room is 25 degrees C (about 75 degrees F).

It also assumes an air mass of 1.5.

Solar Panel

2011-09-08T16:43:00.000-07:00

A solar panel is a modular housing unit, enclosing photovoltaic cells and containing wires to connect power into a solar electrical system.

Panels are rated by their performance in Standard Test Conditions (STC). STC is the method of determining comparative performance of solar panels fairly.
Included:

VOC open circuit voltage
VMP max. power voltage
ISC short circuit current
IMP max. power current

Air Mass

2011-09-08T16:40:00.000-07:00

Air mass is the thickness of atmosphere that the sunlight must penetrate in order to reach the panels. The more direct the sunlight, the less air mass. In the illustration to the left, you can see that the sunlight is more direct at (b).

In STC, air mass is accounted for as a factor of 1.5.

Amps And Volts

2011-09-08T16:34:00.000-07:00

Difference Between Amps and Volts
Understanding the basics of electricity

In order to understand series/parallel wiring, it becomes necessary to understand the concepts behind electricity.

Electricity has two components: amperage and voltage. As a comparison, you can consider voltage to be the pressure of the flow of electrons, while amperage is the size of the field, as demonstrated by this visual description.

You can adjust the voltage and amperage of your array in the way that it's wired.

Further Reading:
Series/Parallel Wiring

Exercise:

Angle and Orientation: Efficiency Table

2011-09-08T16:30:00.000-07:00

You can expect a different percent of production from your array, depending on its position.

The "Orientation" of a solar array defines whether it is facing south, southeast, and so forth. Essentially, what part of the horizon the panels are facing. It's favorable in the northern hemisphere to have panels facing south. The closer to South you are, the better the system performance.

The "Angle" is whether the panels are flat or vertical, or anywhere in between. It benefits the system to have the panels roughly 15 degrees less than your latitude. In other words, in CT where latitude is about 38, it's beneficial to have the panels at about a 25 degree angle.

As demonstrated in the table, you can see what the difference between panels that are 30 and 15 degrees in angle will produce, comparatively.

Magnetic Declination

2011-09-08T16:21:00.000-07:00

Depending on where you are, a magnetic compass may be incorrect because of differentiations in the Earth's magnetic field.

Why This Matters

This is important to consider, when using a compass, because your estimation can be off by the amount of degrees that should be accounted for in magnetic declination.

In America, the declination never reaches beyond 15 degrees. Check out the graphic to the left, and it will give you a better idea of some of the declination factors around the world.

Affects: Panel Orientation

Question: What's your area's degree of magnetic declination? How much does it affect system production by accounting for it?

Irradiation Data and PV Calculators

2011-09-08T16:02:00.000-07:00

National Renewable Energy Laboratory
information on solar irradiation

You can find some excellent information on how much sun is available in different parts of the country by visiting this website.

[Get Solar Radiation Data]

PV Calculator
Online Estimation Tool

This website will perform many of the calculations taught on this website, for free in a simple to use form that you complete with your information.

It's a little more convincing to do the calculations yourself, but many of the methods of estimating your home's potential for solar electricity are used by this calculator.

[Enter the PV Watts Calculator Page]

The Line/Load Blog helps explain how to use this data for the purpose of developing your own estimates for solar productivity in your home.

Other Works Referenced

Nabcep Study Guide.

Marks' Standard Handbook for Mechanical Engineers

Main Service Panel

2011-09-08T15:13:00.000-07:00

All homes have main service panels. It is your home's electrical power distribution center. If any of the circuits in your home are overloaded, this is where you must go to reset the breaker and get things running again. Circuit breakers are housed inside of service panels and are designed to prevent circuits from overloading the wires that transfer the electrical energy to the components requesting the energy.

There is a rule for determining if your service panel is sufficient for solar power. It's a bit complicated, but you can read how much solar your home's electrical system can handle, without any major upgrades, over here.

Solar electrical systems are wired into the main service panel, just like any other device. The difference, however, is that the solar electrical system provides power, while most appliances consume energy.

main service panel, to the left in this photo.

Mounting System

2011-09-08T14:43:00.000-07:00

There are a number of different kinds of mounting systems. These are all listed above. The panels need to be attached to a structure in some way, shape or form, right? That's what a mounting system does. It attaches the panels to the structure they're mounted on.

Types of Mounting Systems

Roof Mounts

Roof mounts come in a few different forms, but they're all fairly similar. Most are made out of aluminum and fasten into the rafters of your home, through the shingles. There are effective ways of getting your roof mount not to leak. The most effective way of accomplishing this is to use flashings for every lag screw that goes through your roof to support a rail footing.

For the most part, the average roof mounting system is essentially connected directly to your home without much leverage in your ability to tilt the panels in any particular direction. You can install tilt mounts on a shingle roof, if you want, and the result can sometimes benefit your annual production. But most people don't install tilts on their homes, even though it's possible, just because it can look something awful.

Flat Roof Tilted Mounts

Most mounting systems that are designed for flat roofs utilize a counter-ballast system. Meaning? Blocks of cement are usually used to keep the mounting systems on the roof in the event of high winds. The rails are connected to trays which hold the blocks.

Ground Mounts

If you've ever seen solar panels out in a field, they're ground-mounted. It's sometimes the same stuff that is used on residential mounts (in fact, all of these rail mounting systems are very similar in the ways that the panels attach). Ground mounts are connected by pouring cement into cylindrical areas around the footings.

Pole Mounts

Pole mounts are different from ground mounts, in the sense that they can be adjusted easily. They contain a part called a "mast" which goes to a series of rails that can hold usually 12 or 16 solar panels.

Some pole mounts are able to track the sun, meaning that motors and sensors make it possible for the array to face the sun at an optimal angle all day. This can have as much as a 20% improvement on the overall production of the system.

Research

Unirac Mounting Systems

WattSun Solar Trackers

Disconnect

2011-09-08T14:24:00.000-07:00

A disconnect is a device that shuts off all flowing power safely in the event of a service call or emergency.

You will find two in a residential PV system. One, located between the panel DC wiring and the inverter. The other, between the main service panel and the inverter.

Sometimes, inverters have built-in disconnects.

Residential power systems rely on the smaller-sized disconnects, which are rated by the amperage they are allowed to handle. They come in 30 amp and 60 amp versions.

What's Your Power Source?

2011-09-08T08:41:00.000-07:00

If you tracked your power source, straight from the outlet in your home that keeps your food cold in the fridge, you will find that there are a number of steps to backtrack in order to find the source.

That power is wired to a Main Service Panel. That's the fuse box in the basement. The main service panel is connected to the power lines around your neighborhood, eventually leading to a transformer that distributes power in your area.

The transformers run eventually to substations, which are connected to large generation plants. These large plants could be Nuclear, Coal, or something renewable like a solar field or a wind farm.

I know that it requires immense amounts of energy, and causes pollution, to create solar panels. But once they're made, you don't have to replace them every year! Maybe once every 25, currently at their level of electrical integrity. Longevity is just as important as efficiency, according to total lifetime power output calculations.

Osha Certified

2011-09-08T08:10:00.000-07:00

I have OSHA Certification.

That means that I know what is required to be safe on a job. This is no substitute for job experience.

OSHA is a common-sense test, and it also requires you to know when to enact which safety system. You also have to know how to construct these safety systems.

Licensed * Experienced * Certified

2011-09-08T08:05:00.000-07:00

Click [here] for a full slideshow of photos I took on installations i led from 2008-2010
Click [here] for more of my thoughts on the future of licensing and solar in CT.

Capable of designing photovoltaic systems of any size.
Designed and installed systems as large as 36kw.

Residential Projects I Managed As Lead Installer:

7KW. Torrington, CT

5 KW. Newington, CT

7 KW. Oxford, CT

Dual Axis Tracking Pole Mount. Coventry, CT

Commercial Projects That I Managed As Lead Installer / System Designer:

30 KW. John Dorr Nature Center, Washington Depot CT

36 KW. Saybrook Point Inn, Old Saybrook CT

I've worked on a ton of projects, but these are a few of my favorites.

I am also Sunpower and OSHA-10 Certified.

Workbooks

2011-09-08T07:32:00.000-07:00

After I learned how to build solar electrical systems, and was concurrently laid off from work (for various reasons), it became apparent to me that I would design a series of instructional materials so that the common homeowner and student would be able to feel confident in the purchase of a solar electrical system.

Right now, there's no better bet you can make than in solar. And that's really true, for so many reasons. It has a 100% guaranteed return on investment, and while that may take as long as 15 years, it will still offer you one less thing to worry about down the road. It also increases the value of your home. What you're probably worried about is not knowing how it will work. Maybe you would like to prove to yourself, mathematically, that a certain number of panels will actually maintain your energy needs, year round. This website will get to that too.

Some of the workbooks help you learn how to estimate solar production. Other workbooks will assist you in learning how to wire the array on the roof. There are exercises that help you understand your consumption, and there are ways i've devised of explaining the difference between amperage and voltage. At some point on the site, I'd like to develop a page that just simply explains how to design a solar electrical board game.

Hey, before anyone really gets in to something, they want to know how it works. Right?

Question. Can Solar Actually Offset Everyone's Electrical Needs?

The answer is no. Truth be told, it can only offset some people's energy needs. It can only offset the needs of the people who invest in and build systems for themselves.

Why "Line / Load " ( ? )

2011-09-08T07:13:00.000-07:00

When I first started performing solar electrical installations, as a journeyman's apprentice, one of the first things I really noticed was how confused the old-school electricians were about the interconnection.

They'd say, "Hey, is that thing on the line or the load side?" And by that they meant, was it drawing power or generating it? To an electrician, an inverter is just like any other 240v electrical device in a home such as a clothes dryer or rangetop stove. At least, it's wired the same.

With that said, there's a practice of keeping the load side of the current tied in to the bottom of a disconnect. They couldn't figure out whether it should be wired to the bottom or the top.

"Isn't that thing generating power?" they'd ask. And we'd say, "Yeah." To that, they'd respond "Well then shouldn't it be wired to the top of the disconnect?"

It was an endless argumentative point of confusion with the old-school electricians. They'd use it as an excuse to get donuts. They'd say, "hey, we're gonna need a cup of coffee and some donuts before we can really figure this out." And then, they'd leave for an hour and come back, tie in the disconnect any which way they wanted, then vanish, not to be seen again until their next subcontracting gig.

Military Bases Get 160,000 Residential Systems Guaranteed

2011-09-07T18:56:00.000-07:00

"The Energy Department said Wednesday it provided a partial guarantee for a $344 million loan to San Mateo, Calif.-based SolarCity for the SolarStrong Project, which seeks to place solar panels on 160,000 homes across 124 military bases in 33 states." (main article)

Recently, it has been reported that the government plans on funding "the largest residential solar project in history."

That's great, but at the same time, doesn't the military get enough funding? I think it's telling, of the times, to say that the greatest investment in residential solar in the United States goes towards the military, as does most of the federal budget.

As convenient as that may be, this doesn't solve anything. Even a certified atheist would have a difficult time not coming across as a religious nut, trying to explain the problems we face, because the situation is immensely complicated, and to many people, the end of the Mall sounds like the end of the world.

If you're in the military and you live on a base, I hope you read this website because you're going to have one of these things on your home probably pretty soon, so you might as well learn what the parts are, and how they work.

Reasons Not To Max Out Roofspace.

2011-08-22T08:52:00.000-07:00

Ok, let's say you got yourself a weird roof. There's nothing normal about it. It's not a square. It's some kind of peculiar shape. There is a way to figure out how many panels are going to fit up there, but it's not going to be as simple as getting the square area and fitting in a number of panels that match that area.
Here is the way that I've come up with that may help.

First of all, panels all have dimensions. Also, panels require mounting systems. Ultimately, the space on your roof has to facilitate the rails.

Start with the longest vertical measurement. That's a good place to start, right?

Get yourself nice and comfortable along the ridge of the roof and run your tape measure down to the gutter. Don't measure exactly from the very top to the very bottom! In fact, if your roof overhangs beyond the structure of the house at the bottom, don't consider mounting onto that part.

Next, draw a series of horizontal lines, perhaps with a crayon onto the shingles. (the lines will wash away in the rain if you make them lightly). Use the dimensions of the panels you intend to use. Here we see that from the top to the bottom, there's enough room for 3 rows of portrait-oriented panels, without enough room for 2 rows to fit at the narrower part on the left. However, if the panels are oriented landscape, three rows will fit.

Don't let someone sell you this. It's too big for the roof. Note the "precise" distance from gutter to the peak. This generally means one of two things. You're either going to see the backs of the top panels from the other side of your house, or the panels at the bottom are going to send rainfall right over your gutter. Possibly both. I know it looks 'great' (yeah right). But in reality, it's impractical to fit that many panels on a roof.

Here is a way more practical approach. There are only 6 fewer panels in this example (the one above is the 'maxed out' version). But in this version, first of all the array will definitely fit on your roof. And secondly, 32 panels will fit onto a single inverter as 4 strings of 8, which is great!

What would the purpose of those additional 6 panels actually equate to? In all honesty, nothing but a bunch of issues. First of all, 38 panels would require you to break your array into 2 separate inverters, because 38 is not divisible by a number of panels that will series into a string that is compatible with an inverter. You'd end up with 2 strings of 10 and 2 strings of 9, probably, each on 4000w inverters. Now you have twice as many inverters, and only 6 more panels.

I guess that's ok, there's nothing exactly wrong with 2 inverters. But additional costs are not just that you're buying twice as many inverters (rather than a single 7kw inverter). You also need an additional subpanel. It might require a service upgrade. Those 6 panels, at STC 1.2kw, are really going to only generate 900w at max power, 1.4 mW a year in an area like Connecticut.

Hmm, that's starting to sound good again. I guess these are the questions we're forced to ask ourselves before we enter a situation like getting a PV installation though... right?

Solar Panel Wiring Box

2011-08-20T08:46:00.001-07:00

On the back of every solar panel, there is a housing unit for the blocking diodes where the leads that come from the panels connect to the cells. Here is an inside look at what that looks like in a Sunpower Panel. The blue arrows point to the blocking diodes. The red arrow points to where a wire should be running from, but as you can see, it's been pulled out by an installer who put too much tension on the wire and pulled it from its connection (I'm not naming any names).

The point of showing you this is to explain the difference between a Panel J-Box and the other places you might see the term J-box (junctionbox). For example, the combiner box could be considered a J-box, but luckily we came up with a neat term for it so you wouldn't get it mixed up.

The Importance Of Safe Harnessing Practices

2011-08-19T15:58:00.000-07:00

Joey Dorwart, in his safety harness pose

The world can look mighty purdy from a rooftop. But It can also be quite dangerous. You're faced with the obvious: an incline that leans in the direction of down, towards a distance that could impair you for life. Fact: falling is a major cause of death in America for workers.

That's why in the 1970's the federal government came up with OSHA: Occupational Safety and Health Administration. Which, for the most part, is a really good idea. There are tons of programs available online to help you become certified with OSHA. For example, OSHA-10 requires ten hours of study time, with each section followed by a comprehensive test.

Many will argue that OSHA does not prepare you for real life. Working on PV installations, and being responsible for the safety of others on the job, I have come across all types of situations. So here is what I suggest for safe and easy solar installation work practices.

In all situations of areas above 6', OSHA requires that you wear a harness and be attached to a rope that is held down with 5000 lbs. of resistance strength. You can't share an anchor with another worker. Each worker needs his or her own personal fall arrest safety system.

This is real talk from a real installer about actual situations. In the company I worked for, we were taught to carry panels on our shoulder up ladders. It wasn't until someone fell off a ladder climbing up with a panel when we started paying more attention to the wind forces present on the job site. We also implemented retractable rope-grabs that we could use while carrying panels up ladders at that point.

Here are a few suggestions to installers out there. I know that OSHA isn't always watching, and the foreman might be pre-occupied. But if you're an installer, and you want to be safe, here are a few rules that will help you live to install another day.

Flat Roofs
In flat roof situations, it's best to have all areas marked off with caution tape, with barriers constructed around the entire perimeter. It's an option that prevents that situation from becoming cluttered with rope.

Roofs 30° or Less
In situations where the roof is not at a steep incline, the best way to handle this from a realistic perspective is to have the safety system completely installed. Have an anchor up there. Wear your harness. Have ropes. It's been my experience, with sure-footed roofers who often take risks that they shouldn't, that it's best to propose a realistic approach than to enforce rules that no one is willing to follow. If you are in a situation where a rope becomes necessary to grab, it's up to your own sensibility to clip in and make that move. It makes it easier if you are already wearing a harness, and the rope is available for you to grab.

When a rope isn't being depended on entirely for support, it can become a tripping hazard for an installer who is more concerned with the task at hand, than the rope that the worker might consider unnecessary, depending on their own self-assuredness.

Roofs 31° or More
36° is around the point where harnessing systems are depended on by installers to keep them from sliding off the roof. A situation where your personal safety system is also your lifeline, and your weight is being held by the rope to keep you from falling constantly, is quite different from one where it's merely to keep you safe in case you accidentally take a major spill or lose your balance and fall off a rooftop.

Mounting system rails are often used as toe boards, supporting installers' weight once they're installed. Often on steep roofs, an installer will assemble and fasten the bottom rails first, so that there is something to stand on as the upper rails are installed. It's important, in those situations, for an installer to recognize that their weight will affect the distance between the two rails by the amount that it bends it downward. If even by a matter of less than an inch, it could affect a mounting system like Sunframe adversely.

Combiner Box

2011-08-19T12:37:00.000-07:00

A combiner box is a junction box on the DC side of the system. This is the point where the solar panels are combined, essentially where the system is electrically connected into a fewer number of circuits through parallel wiring.

If this is confusing, maybe it could be explained a little better. This part of the system requires an understanding of voltage and amperage, but it's fundamental in understanding how panels are wired. Every system with more than 2 strings require a combiner box, whether it's located at or within the inverter, or higher up near the array.

Benefits Of Combiner Boxes
Many installers use combiner boxes as an opportunity to change the wiring from outdoor-rated USE-2 wire, to the conduit-insulated THHN or similar, which can fit more comfortably in the EMT that is required. It's also a chance to fuse a system upon entry to a building, which is a smart move, from the perspective of fire safety.

Read More:
Combiner Box Assembly

Amperage

2011-08-19T12:15:00.000-07:00

Amperage is a measurement of the strength of the current in electricity. When multiplied by voltage, it gives you the wattage of the electrical energy. Many devices, such as inverters and disconnects, are rated by their ability to handle different amounts of amperage. Circuit breakers are rated by amperage.

Voltage

2011-08-19T12:13:00.000-07:00

Voltage is a measurement of pressure in electricity. Multiplying voltage and amperage allows you to calculate wattage. Most PV systems have a maximum voltage of 600. Most inverters have voltage thresholds of 250-550v DC. House electricity is 120/240v AC.

Hold-Down Strength

2011-08-19T11:38:00.000-07:00

Hold-Down Strength is the ability of the array to stay connected to the structure it is installed on, in resistance to the wind speed of that area. This can be made either by counter-ballasting the system, or by fastening it to supports with large screws, known as lags.
Read More:
Calculating Hold-Down Strength (technical)

Sizing an Inverter To A Service Panel

2011-07-20T09:01:00.000-07:00

Let's say that your home's existing electrical system contains a main service panel that has a busbar rating of 200 amps. The busbar rating is listed on the door of the panel. Most houses' service panels are either 100 or 200 amps, unless you have something old and funky, or massively huge.

Every house electrical system has a main breaker. That breaker has a rating, whether it's 200 amps or 250 amps. That is the point at which the load from your house will shut off the power for safety.

To determine the amount of backfed solar power your house can withstand, there's a really simple calculation you can perform, and it's extremely simple.

Take the rating of the busbar. Multiply it by 120%. Subtract the main breaker.

Busbar = 200 (x120% = 240) - Main Breaker (200) = total of 40 amps to backfeed onto.

let's say it's a 225 amp panel, and a 200 amp main breaker.
225 (x120% = 270) - Main Breaker (200) = total of 70 amps to backfeed onto.

What does that mean?
If you can backfeed 40 amps, then multiply the 40 amps by the house power coming in. That means you can have 7,680 watts backfed into the house, because 40 amps at 240v AC is 9600w. But then you must divide by 125% for overcurrent protection, leaving you with the 7680 watts, or at most a 7000-watt inverter that can tie into the existing home electrical system.

Can you lower the rating of your main breaker?
Yeah, technically you can but it's not recommended. It's better to upgrade your service panel.

What's a Line-Side Tap?
Please don't ask that question.

Consumer Advocacy

2011-05-27T08:09:00.000-07:00

If you are interested in learning more about Solar Electricity, and want the advice from an unbiased, trained professional, then look no further!

Using the methods described in this site, I can determine the following information from visiting your site, whether it's your home, business, or backyard:

1). How many panels can fit
2). Whether your roof can support a system
3). Whether your existing electrical is sufficient for a PV system
4). Advice about the best equipment options
5). Recommended Installers

Fact: Many installation companies have sales people who double as system designers. Their own personal interests aren't served by giving the most accurate information possible. By having an independent firm, such as Stereo Solar, enter into the equation, you ensure that your system is designed accurately.

Let's say that you want to have a system designed for your home. You want quotes from 4 different reputable solar electrical installation companies. Each team comes to your home, visits, gets on your roof and measures, goes back to their respective offices, and returns to you a plan and a quote.

You're not sure why the 4 plans are different. Some of them contain different components, none will really involve you into the decision process, nor consult back with you on the decisions in the design.

What You Receive

Home Visit

Roof Measurement
Shade Reading Using Pathfinder
Existing Electrical System Evaluation
Roof Structural Assessment
Electrical Bill Analysis
All Questions Answered By Licensed Solar Electrician.

System Design And Annual Estimate

How many panels can fit on your roof
The inverter that matches the hypothetical roof array
Additional electrical components (disconnects, conduit, wiring)
What kinds of home modifications might be necessary
How much power that will provide your home every year (in KWH with a +/-10% margin)
How much money it should save you annually (assuming 5% annual increase of electricity costs).

Bidding With Installers

Recommendations with reputable installers on the CCEF List of Approved Contractors
Providing multiple companies with your information so that they can bid on the project.
Getting you the best estimates possible.

More Reasons To Get Your Home Evaluated Independently By A Professional

Even if the rebate conditions are not ideal, it's still a good idea to get a system designed. When rebates return, many installers will be swamped with inquiries for site surveys. If you already have the information available, then your installation process will be expedited when the rebates become available again.
You might discover that the cost is affordable right now, without even knowing it. The only way you'll know is by having a site survey!
My designs are professional. I have extensive experience as an installer. I have also created this website to further evidence the transparency that I wish for solar energy to convey to the public.
Your house isn't going to change size, orientation or angle ever. In other words, you only need to have your home evaluated for solar electrical systems once. If the panels increase in efficiency, the estimates can be re-evaluated to match those improvements in technology later.

Current Cost: $250.
Includes visit, design, estimate, and submission of plans to installers for bids.

Email StereoSolar@Gmail.Com or call 203.745.9452

This is the way that your purchase of a Solar Electrical System would normally work, without the help from hiring an accomplished system designer privately. Can you imagine the time and effort required, dealing with a different plan per every installation company you contacted? The Site Survey service is worth just the time it saves.

Not to mention, you're getting an unbiased report on your home's available photovoltaic potential, without the influence of a salespersons' commission influencing the size or type of equipment that an installer might offer.

Flashing and Roof Penetration

2010-10-18T22:25:00.000-07:00

This is a classic photograph on a brisk winter morning, of what a flashing looks like when it's properly installed on a roof. Note how the shingle is cut at the right point, and the rubber gasket fits all the way around the LB pullpoint.

Also, you might notice how there's wire that is suspended, coming out of it. Those wires are held above the roof surface using zipties and tension on the groundwire. The code violation here is the tension being placed on the grounding conductor. The alternative? None was ever offered, and none was given. It might have been considered OK if we used a different wire to hang the other wires by its tension. As long as that particular wire wasn't a conductor of any kind. But that would just seem a bit odd, considering that we were already under certain time constraints, and it would also be a questionable use of additional copper.

Room Full Of Inverters

2010-10-18T22:19:00.000-07:00

Each of these inverters is equally spaced with enough distance for their fans to work. At least, as spaced as possible with the dimensions of the room.

The room used to be the servant's closet in the top floor of the Saybrook Point Inn. There's really no indication to anyone where this room actually is, although there should be a map to it somewhere. Luckily, Nick the Super is a superhuman being.

additional information
There's 3 inverters on the left wall, each feeding 24 x 305w SPR modules facing east, totalling 72.
Then there are 2 inverters directly in front, which feed 24 x 305w SPR facing west (48 panels).
Finally there's a 6th inverter on the wall facing, which has a single 24-panel array, same panel.

What's the total number of panels on that installation?
What's the VOC rating with temperature adjusted for -24°c?

Private Testing Programs

2010-10-18T21:54:00.000-07:00

Let's face the facts, here. Nabcep is nothing more than a private enterprise, centered around collecting money from people. I would believe otherwise, if they were differently structured. But all indications point to lead towards Nabcep standing not for education, not for workforce preparedness nor usefulness to the industry as a whole. I think it's just a way for a few people to make a bunch of money.

If the Department of Energy (Energy.Gov) were to step in, the test would work drastically differently from NABCEP's. First of all, it would only contain questions relevant to the average workers' experience. Many of the key questions in the Nabcep exam are based on the hardest questions ever faced by anyone in the industry. And their answers are pretty much the opinions of the people who were asked the questions by real life experience in the first place. Nobody truly understands the way that electricity works. We're still learning about it everyday, and yet the Nabcep exam claims, in its questions, to know the best solutions to the most unanswerable problems that PV could ever deliver.

I say leave those questions to the few and far between us who might be faced with them on occasion. The average solar workers' experience contains boundless amounts of information to be memorized, none of it as specialized as Nabcep. Some of which is asked on their test, often where the phrases are oddly structured and the true nature of the question is difficult to determine.

To me, that's by design. I know that tests aren't supposed to be easy, but the Nabcep test is designed to fail, solely for the reason that they can charge you to take it over again. In fact, you have a much better chance of passing it if you invest in one of their official preparation classes, where the instructor is given precursory language to explain the meaning behind the next batch of tests to the students.

To me, that's not capitalism, and I believe that's where we draw the line. The point at which capitalism ends is not socialism. It's exploitation. And this is an exploitative technique, as many techniques currently exist within the industry, to keep knowledge of the field to a minimum. There's no shortage of interest in the study of solar electricity, but society almost intentionally keeps itself apart from the information necessary for we, as a nation, to move forward with alternative energy.

Solutions

I believe that the first, and probably the best, solution is this. The US Government needs to step up and create a federal certification (not a license but a certification) to prove to others that "this individual is capable of estimating the production of a PV array annually."

And I'm not talking about just one time showing what the scores are. I'm saying that individuals could take this test multiple times, getting higher scores in different areas each and every time they take it. I'm also suggesting that the DOE publish the results of the test, for those who wish their test scores to be seen. This would give people an indication of the level of understanding an individual has, in that particular field. Much of this, though, is hypothetical.

Because in reality, the rules of on the job preparedness for PV solar are still, despite the booming success of the late 2000's for solar, extremely primative. Nabcep certainly isn't doing the trick, and I would be skeptical for any institution, even my own, for providing students with credentials that evoke confidence in people who are looking for others to hire in order to install photovoltaic grid-tied backfeeding systems.

Solar Credentials in CT: A Summary

2010-09-26T10:14:00.000-07:00

As of September 20 2011, in Connecticut there are only:

10 people in with PV-2 licenses,

15 people in with PV-1 licenses

[search here]

and

17 people in with Nabcep Certification.

[search here]

What does this mean?
These kind of certifications qualify individuals to design and lead solar PV installations. In order to implement solar electrical energy on a mass scale, more people need to qualify with licenses to ensure that homeowners are getting proper estimates, and systems are installed correctly.

What if you're a regular electrician?
Ordinary electricians with normal training are well-versed in AC wiring, and can learn the DC wiring of systems with relative ease. The construction aspects of PV systems are slightly out of the normal range of an electrician's experience, and the design and estimation techniques are never touched upon in normal electrical training.

Why Certify?
I have proposed to the state board of licenses to offer an additional PV endorsement test for licensed electricians, such that they will become certified PV electricians through the process of reviewing material and passing a test that proves:

That these electricians understand NEC 690 and can answer questions like which is the ungrounded conductor, wire sizing for PV systems (voltage drop at <1%)
That these electricians understand waterproofing methods, aspects of roofing, can calculate hold-down strength and uplift potential, as well as dead load, and weight distribution.
That these same individuals can estimate the annual production of a PV system based on the methods described here in this website.

This website contains the relevant information that will help an electrician perform these calculations. Electricians should be tested on this material because it ensures:

The longevity of the system
The safety of the installation
The accuracy of the estimate

Something to consider.
click image to search!

CCEF Finance / Investment Authority

2010-09-22T11:16:00.000-07:00

In Connecticut, there is a central government agency that grants contractors the right to have access to the state funding.

Currently, that list contains 74 installation companies for solar electrical installations, and this list is available at the bottom of this post.

Right now, of those, only 29 contain endorsement for the Solar Lease, which is a system of finance that does not allow you to own the system that you install until after 15 years, where you're given the option to buy it.

[The CCEF list of approved installers PDF] sept 15 2011 updated